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CATEGORIES:Electronic Structure Discussion Group
SUMMARY:Accelerating linear-scaling DFT: Differential geo
metry meets electronic structure theory - David O'
Regan (TCM)
DTSTART;TZID=Europe/London:20101117T110000
DTEND;TZID=Europe/London:20101117T114000
UID:TALK21833AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/21833
DESCRIPTION:The use of nonorthogonal functions to support sing
le-particle states is ubiquitous in contemporary d
ensity functional theory\, indeed\, it is practica
lly obligatory if one wishes to construct a method
for which the effort scales with system size. As
a result\, it is of increasing importance to under
stand the measures which must be taken to accommod
ate it. In this talk I will begin by going "back t
o basics"\, exploring the consequences of support
function nonorthogonality and attempting to shed l
ight on the accompanying notation and terminology
so often used by linear-scaling DFT practitioners.
\n\nFor many tasks we may wish to change the suppo
rt functions during the course of a calculation. F
or example\, in ONETEP a set of nonorthogonal gene
ralised Wannier functions (NGWFs) are optimised to
accurately minimise the total energy\, in DFT+U t
he nonorthogonal Hubbard projectors may be made co
nsistent with the NGWFs (projector self-consistenc
y) or optimised to meet another criterion such as
providing a maximal the U tensor\, and in linear-s
caling TDDFT one may wish to propagate the support
functions in time in order to achieve plane-wave
accuracy. I will analyse the consequences of suppo
rt function optimisation in each of these cases on
geometric grounds and\, on that basis\, demonstra
te a first-principles method to improve both the n
umerical stability and speed of such calculations.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
CONTACT:Dubois Simon
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